Intelligent Transportation Systems (ITS) endeavor to improve safety and efficiency on roadways by adding intelligence to moving vehicles and also to fixtures on and around roadways. There are many different functions and purposes that could be enabled by ITS. Some of these include managing traffic flow and lane occupancy, collecting tolls, tracking freight, providing road condition alerts, alerting about pedestrians and other obstacles on the roadway, and the like. In addition to intelligent vehicles and fixtures, ITS seeks to allow vehicles to communicate with other vehicles and with other proximate devices on or near the roadway.
The Wireless Access in Vehicular Environments (WAVE) architecture and standards have been developed to support ITS safety and non-safety applications. Most ITS applications rely on the concept of situational awareness by the vehicles and the fixtures that is then enhanced by a co-operative awareness. The co-operative awareness is based on periodic and event-driven broadcast of basic safety messages (BSM) between vehicles (i.e., vehicle to vehicle (V2V) communication), between vehicles and infrastructure fixtures (i.e., vehicle to infrastructure (V2I) communications), and between vehicles and pedestrians (i.e., vehicle to pedestrian (V2P) communications). Collectively, V2V, V2I, and V2P communications are designated as vehicle to everything (V2X) communications.
In several ITS scenarios, Road Side Units (RSUs) are defined as communication nodes that are able to provide safety services (e.g. interaction collision warning) and non-safety (mobility information) services to vehicles and to other RSUs through broadcast messages.
V2X communications are provided in part by a dedicated short range communications (DSRC) channel, which may be carried by a local and metropolitan area network such as defined in the IEEE 802.11p standard and by a cellular network (e.g., long term evolution (LTE), fifth generation (5G), etc.). The 802.11p standard may use channels of 10 MHz bandwidth in the 5.9 GHz band (5.850-5.925 GHz). The DSRC may be one or more one-way or two-way short-range or medium-range wireless communication channels that are specifically designed for automotive vehicles. V2X devices may be equipped with multiple radios operating in different spectrum bands. Cellular networks may be used to assist V2X devices to discover and take advantage of safety and non-safety services, which may be broadcasted over one or more DSRC channels.
In order to send and receive messages in a DSRC 802.11p wireless local area network, a device (e.g. RSU or vehicle) sets up or discovers and joins a WAVE basic service set (WBSS), which is a basic service set (BSS) where devices may operate in the WAVE mode and may communicate without the need to execute the typical 802.11 authentication and association procedures. In order to discover a given WBSS, V2X devices scan multiple DSRC channels for messages from that WBSS. The WBSS will be identified by a BSSID (Base Station Subsystem Identification) in the 802.11 MAC (Media Access Control) layer frames.
The deployment of DSRC/802.11p-based Road Side Units (RSU) may involve large investments in roadway infrastructure due to coverage limitations of the 802.11p standard. Existing cellular systems, such as LTE, are being considered as an alternative to DSRC/802.11p for ITS applications given its large scale coverage and efficient spectrum utilization. The LTE Proximity Services (ProSe) functionality is being considered for enabling ITS use cases through direct device communications.